release: Add CONFIG_NEWLIB_LIBC_USE_POSIX_LIMITS_H to release notes

Add new config for CONFIG_NEWLIB_LIBC_USE_POSIX_LIMITS_H to release
notes.

Signed-off-by: Al Semjonovs <[email protected]>

Author: asemjonovs

doc/releases/release-notes-4.3.rst

@@ -179,6 +179,10 @@ New APIs and options
     * :c:func:`zsock_listen` now implements the ``backlog`` parameter support. The TCP server
       socket will limit the number of pending incoming connections to that value.
 
+* Newlib
+
+  * :kconfig:option:`CONFIG_NEWLIB_LIBC_USE_POSIX_LIMITS_H`
+
 * Power management
 
    * :c:func:`pm_device_driver_deinit`